Because pressure sensors that take advantage of a semiconductor's piezoresistive effect are compact, lightweight, and highly sensitive, they are widely used in the fields of industrial measurement, medical care, and the like. In such pressure sensors, a diaphragm is formed on a semiconductor substrate. Furthermore, a strain gauge is formed on the diaphragm. When pressure is applied to the diaphragm, the strain gauge deforms. The piezoresistive effect allows any change in the resistance of the strain gauge to be detected, and thereby the pressure is measured.
A monolithic pressure sensor that provides a differential pressure diaphragm and a static pressure diaphragm on the same substrate has been disclosed (refer to Japanese Unexamined Patent Application Publication No. H5-72069 (“JP '069”)). In this disclosure, strain dividers are formed between differential pressure strain gauges and static pressure strain gauges. Forming these strain dividers ensures that, when static pressure is applied, the stress generated by the static pressure diaphragm spreads to and affects the differential pressure diaphragm, which prevents the applied pressure from affecting the differential pressure measurement value. For example, when a differential pressure is applied, the change in the differential pressure diaphragm generates excess stress on the sensor chip. This stress affects the static pressure gauges. In addition, when static pressure is applied, the change in the static pressure diaphragm generates excess stress on the sensor chip. This stress affects the differential pressure gauges. The strain dividers mitigate these impacts.
In addition, a pressure sensor of another configuration has been disclosed (refer to Japanese Patent No. 3359493 (“JP '493”)). This pressure sensor adopts a structure wherein appropriate nonbonded regions are provided at the corners of the surface of the sensor chip to which a pedestal is bonded. Specifically, a differential pressure diaphragm is formed in a center part of the sensor chip, and nonbonded regions are formed in the corner parts of the sensor chip. Thereby, temperature-induced zero shift and the attendant dispersion is minimized, which makes it possible to provide satisfactory temperature characteristics.
Nevertheless, in JP '069, if the sensor chip is made compact, then sufficient space for providing the strain dividers must still be secured, which is a problem. Namely, the strain dividers themselves increase the size of the sensor chip. In addition, if the configuration recited in JP '493 is adapted to the monolithic pressure sensor, then securing spaces to form the nonbonded regions in the corner parts of the sensor chip becomes difficult.
Thus, it is difficult to implement a compact, high performance pressure sensor, which is a problem.
The present invention was conceived to solve the aforementioned problems; it is an object of the present invention to provide a compact, high performance pressure sensor.